The augmentor duct of a gas turbine engine conveys hot gas in the order of 2500 F. temperature. This is often passed through variable convergent divergent nozzles to discharge. Even with seals at the interface of the flaps of the nozzle some hot gas may leak out.
Fuel fumes from the engine compartment can create explosion potential within the aircraft structure. Attempts have therefore been made to provide additional sealing between the hot gas and the engine compartment.
Weight is a serious concern in an aircraft engine. It accordingly is desirable to use lightweight structure. Such lightweight fairing structure may be easily deformed to the point that it interferes with the nozzle flap drive. This interference may disable the drive or may further deform the fairing structure to allow the leakage which it was intended to prevent.